Split the seen_metadata function & assign tuple() as default value

src/python/grpcio/grpc/experimental/aio/_call.py

@@ -280,7 +280,7 @@ class UnaryUnaryCall(Call, _base_call.UnaryUnaryCall):
 
     # pylint: disable=too-many-arguments
     def __init__(self, request: RequestType, deadline: Optional[float],
-                 metadata: Optional[MetadataType],
+                 metadata: MetadataType,
                  credentials: Optional[grpc.CallCredentials],
                  channel: cygrpc.AioChannel, method: bytes,
                  request_serializer: SerializingFunction,

src/python/grpcio/grpc/experimental/aio/_channel.py

@@ -101,6 +101,9 @@ class UnaryUnaryMultiCallable(_BaseMultiCallable):
         if compression:
             raise NotImplementedError("TODO: compression not implemented yet")
 
+        if metadata is None:
+            metadata = tuple()
+
         if not self._interceptors:
             return UnaryUnaryCall(
                 request,

src/python/grpcio/grpc/experimental/aio/_interceptor.py

@@ -106,8 +106,7 @@ class InterceptedUnaryUnaryCall(_base_call.UnaryUnaryCall):
     def __init__(  # pylint: disable=R0913
             self, interceptors: Sequence[UnaryUnaryClientInterceptor],
             request: RequestType, timeout: Optional[float],
-            metadata: Optional[MetadataType],
-            credentials: Optional[grpc.CallCredentials],
+            metadata: MetadataType, credentials: Optional[grpc.CallCredentials],
             channel: cygrpc.AioChannel, method: bytes,
             request_serializer: SerializingFunction,
             response_deserializer: DeserializingFunction) -> None:

src/python/grpcio/grpc/experimental/aio/_typing.py

@@ -20,6 +20,7 @@ RequestType = TypeVar('RequestType')
 ResponseType = TypeVar('ResponseType')
 SerializingFunction = Callable[[Any], bytes]
 DeserializingFunction = Callable[[bytes], Any]
-MetadataType = Sequence[Tuple[Text, AnyStr]]
+MetadatumType = Tuple[Text, AnyStr]
+MetadataType = Sequence[MetadatumType]
 ChannelArgumentType = Sequence[Tuple[Text, Any]]
 EOFType = type(EOF)

src/python/grpcio_tests/tests_aio/unit/_common.py

@@ -12,13 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from grpc.experimental.aio._typing import MetadataType, MetadatumType
 
-def seen_metadata(expected, actual):
+
+def seen_metadata(expected: MetadataType, actual: MetadataType):
+    return bool(set(expected) - set(actual))
+
+
+def seen_metadatum(expected: MetadatumType, actual: MetadataType):
     metadata_dict = dict(actual)
-    if type(expected[0]) != tuple:
-        return metadata_dict.get(expected[0]) == expected[1]
-    else:
-        for metadatum in expected:
-            if metadata_dict.get(metadatum[0]) != metadatum[1]:
-                return False
-        return True
+    return metadata_dict.get(expected[0]) == expected[1]

src/python/grpcio_tests/tests_aio/unit/interceptor_test.py

@@ -546,14 +546,11 @@ class TestInterceptedUnaryUnaryCall(AioTestBase):
 
             async def intercept_unary_unary(self, continuation,
                                             client_call_details, request):
-                if client_call_details.metadata is not None:
-                    new_metadata = client_call_details.metadata + _INITIAL_METADATA_TO_INJECT
-                else:
-                    new_metadata = _INITIAL_METADATA_TO_INJECT
                 new_details = aio.ClientCallDetails(
                     method=client_call_details.method,
                     timeout=client_call_details.timeout,
-                    metadata=new_metadata,
+                    metadata=client_call_details.metadata +
+                    _INITIAL_METADATA_TO_INJECT,
                     credentials=client_call_details.credentials,
                 )
                 return await continuation(new_details, request)
@@ -566,13 +563,13 @@ class TestInterceptedUnaryUnaryCall(AioTestBase):
 
             # Expected to see the echoed initial metadata
             self.assertTrue(
-                _common.seen_metadata(_INITIAL_METADATA_TO_INJECT[0], await
-                                      call.initial_metadata()))
+                _common.seen_metadatum(_INITIAL_METADATA_TO_INJECT[0], await
+                                       call.initial_metadata()))
 
             # Expected to see the echoed trailing metadata
             self.assertTrue(
-                _common.seen_metadata(_INITIAL_METADATA_TO_INJECT[1], await
-                                      call.trailing_metadata()))
+                _common.seen_metadatum(_INITIAL_METADATA_TO_INJECT[1], await
+                                       call.trailing_metadata()))
 
             self.assertEqual(await call.code(), grpc.StatusCode.OK)